The present invention relates to radio antennas and more particularly to enhanced bandwidth tactical antennas which are capable of efficiently radiating energy over a broad range of frequencies.
The radio antennas which are used in modern applications such as frequency hopping systems are often required to operate over a range of frequencies. Since the monopole antennas commonly employed on tactical applications typically are electrically short (have mechanical length less then 1/4 wavelength) and have a narrow bandwidth, the impedances of such antennas may easily become mismatched with their transmitters leading to serious losses in efficiency. Hence, antenna coupling systems employing tunable high voltage load coils have been developed which tune these antennas for resonance when antenna length is less than one-quarter wavelength of the operational frequency. Such coupling arrangements result in narrow band tuned conditions which must be adjusted for every change in frequency in order to assure efficient power transfer and further result in high voltage levels under conditions where mismatches do occur. Since antenna coupling systems are relatively slow in executing the retuning function, such couplers do not always provide an adequate solution to antenna tuning for applications such as frequency hopping systems.
It is therefore, an object of the present invention to provide an electrically short tactical antenna system which has inherently broad bandwidth characteristics in radiating radio frequency energy in order to simplify antenna coupling requirements.
It is a further object of the present invention to provide a broad bandwidth electrically short antenna system which lowers the voltage levels on the antenna coupling network due to impedance mismatches between the antenna and the transmitter.
It is another object of the present invention to provide an electrically short monopole antenna system which is simple and inexpensive to construct, yet has a comparatively uniform driving point impedance over a broader range of operating frequencies.